The testing or monitoring of the reliability of exhaust gas aftertreatment systems currently used in motor vehicles requires sensors by which the particle concentration in the combustion exhaust gas can be ascertained precisely, even during long-term operation. In addition, the use of such sensors should enable a loading prognosis of, for instance, a diesel particulate filter installed in an exhaust gas system, in order to attain a high degree of system safety and thereby allow the use of more cost-effective filter materials.
A sensor for detecting particles in a fluid flow is discussed in DE 10 2005 003118, the sensor being developed on the basis of a ceramic multi-layer substrate. It includes two measuring electrodes, set apart from one another, which are exposed to the combustion exhaust gas that is to be tested. If soot is depositing between the two measuring electrodes, this will produce a current flow between the measuring electrodes when a voltage is applied to the measuring electrodes. A heating element, designed in the form of layers, makes it possible to rid the electrodes and their surroundings of deposited soot particles via a thermal process. The sensor also includes a temperature-measuring element that can detect the temperature of the sensor. The heating element is located within the layer composite of the sensor, between the temperature-measuring element and the measuring electrodes. A disadvantage of such a structure of the sensor is that conventional temperature-measuring elements of ceramic sensors have resistor tracks that exhibit increased electric resistance, which can be produced only by complicated production methods such as photo fine-structuring methods, for example.